Chief Cabinet Secretary Osamu Fujimura said cabinet ministers would convene as early next week to discuss ways to bolster cyber security.

"The government would like to unite and take possible measures against cyber attacks," he said.

The National Information Security Center said details on what will be discussed have yet to be decided.

Mitsubishi Heavy, which works closely with Boeing , said this month network information such as IP addresses may have been leaked but so far it has not confirmed any leaks on its products or technologies.

An outside contractor is now checking whether any sensitive data had been breached.

Mitsubishi Heavy delayed reporting the incident to Japan's defence ministry in a possible violation of its military supply contracts.

Rivals IHI Corp and Kawasaki Heavy Industries have said they have received suspicious e-mails tainted with viruses.

It is unclear who was responsible for the attacks.

Similar attacks earlier this year, which included one on the U.S. defence industry, were said to have originated in China.

Chinese authorities have denied having anything to do with those or the latest ones reported in Japan.